Screeding devices or machines are used to level and smooth uncured concrete to a desired grade. Known screeding machines typically include a screed head, which includes a vibrating member and a grade setting device, such as a plow and an auger device. The screed head is vertically adjustable, such as in response to a laser leveling system, to establish the desired grade at the vibrating member. Examples of such screeding machines are described in U.S. Pat. Nos. 4,655,633; 4,930,935; 6,227,761; 7,044,681; 7,175,363 and 7,396,186, which are hereby incorporated herein by reference in their entireties.
The plow is disposed in front of the auger device, which is disposed in front of the vibrating member. The plow typically has a sharp edge that cuts into the uncured concrete surface to establish the desired grade ahead of the auger. Because of the tendency for the sharp-edged plow to catch and drag stones and aggregate, the plow height is typically about one half inch or more above the grade of the auger to limit any grooves or channels caused by the dragging stones from being too deep for the auger to correct.